Agitation device



Sept. 23, 1958 D. s. CUSI AGITATION DEVICE Filed D66. 7. 1954 INVENTOR DANTE s 008/ ATTORNEY nited States Patent 9 AGITATION DEVICE Dante S. Casi, Mexico City, Mexico, assignor to International Pulp Products, Inc., Washington, D. (3., a corporation of Panama Application December 7, 1954, Serial No. 473,611

Claims. (Cl. 259-96) This invention relates to apparatus for subjecting liquidsolid mixtures to an intense mechanical agitation. The apparatus is useful for many purposes as, for example, in the aid of mechano-chemical reactions, a typical use being in the paper industry as a pulper for converting a charge of liquid and cellulosic or other fibrous material into a pulp suitable for use in paper making.

The primary object of the invention is to reduce the power consumption demanded by such apparatus. In accordance with the preferred embodiment of my invention a rotor, submerged in a solids-liquid suspension, is

, formed on its under surface with a chamber for the reception of gas which is retained as a layer intervening between the under rotor surface and the surrounding liquid for relieving certain areas of the rotor surface of frictional contact with the surrounding liquid, in cooperation with passages for the conducting of liquid air mixtures in proximity to the rotor in a manner and for a purpose which will appear.

In the drawing:

Fig. l is a vertical section of my apparatus;

Fig. 2 is a detail vertical section of certain parts on enlarged scale, and

Fig. 3 is a plan View of the rotor showing a modification.

Referring to the drawing, the vessel has side walls 12 and a bottom 14 meeting, in the embodiment illustrated, in the curved portion 16. The vessel shown is vertically disposed and suitably supported.

Within the vessel, in its lower portion, is the rotor disc horizontally disposed and secured as by key 22 to shaft 24 entering the vessel through stufling box 26 to minimize leakage of the liquid contents of the vessel around the shaft. The shaft is suitably supported as by the bearings 28 and is power driven so that the rotor 20 rotates at a high rate of speed.

The upper surface of the disc is formed with a plurality of blades or vanes 30 which may extend radially, as indicated in Fig. 1, or they may be disposed at an angular inclination, as indicated at 30a in Fig. 3, or in any of the conventional ways employed, for example, in pulpers used in the pulp and paper industry. Fig. 3 also shows a second series of vanes 30b disposed toward the axis of the shaft, although this is a modification which may or may not be employed. The function of the vanes, as is well known, is to induce an intense mechanical agitation in the solids-liquid suspension in which the rotor is rotated at high speed, effecting a vortex-like circulation in the vessel as indicated by the arrows 34.

In accordance with the preferred embodiment of my invention illustrated in the drawing, the rotor is formed with an annular depending flange 50, preferably at or adjacent the periphery of the disc, forming a chamber 52 on the under surface of the disc. Into this chamber protrudes a pipe 54, suitably valved as at 56, to conduct air or gas under pressure into the chamber 52.

The rotor 20 may be of the order of 6 feet or more in diameter in some installations. It is surrounded by a fixed annular member 60 formed of a horizontal flange 62 and a vertical flange 64 integrally joined and merging with each other at right angles. The member 60 is mounted in stationary position in the vessel and its vertical flange 64 is spaced from the vertical flange 50 of the rotor to form a cylindrical annular chamber 70. Superposed on the horizontal stationary flange 62 of the member 60 is a ring 72 of hardened material, replaceably mounted on the member 60 a by bolts 74 and extending horizontally inwardly into close proximity to the outer edges 76 of the vanes 30 with minimum operating clearance therefrom. The plane of the upper surface of the stationary horizontal flange 62 preferably lies in the plane of the upper surface of the rotor disc 20 so that the ring 72, being superposed on the flange 62 has its lower surface in the plane of the upper surface of the rotor disc 20. The inner edge of the ring 72 is beveled to aflord a restricted annular opening 71 between the ring 72 and the outer periphery of the upper surface of the disc 20. The arrow 80 shows flow of material therethrough in a manner to be described.

The vertical flange 64 of the member 60 extends downwardly below the plane of the bottom of the flange 50 into proximity with but spaced from the bottom 14 of the Vessel to form a passage 81 therebetween. The arrow 82 indicates the flow of material through this passage.

The horizontal flange 62 of the member 60 protrudes into proximity with the side wall 12 of the vessel but is spaced therefrom to form a further annular passage 83. Arrow 84 indicates flow of material therethrough.

With the apparatus constructed as above described its operation is as follows:

Conveniently the liquid component of the charge is first led into the vessel and the rotor is then started. This induces the vortex-like circulation which is indicated in the drawing by the several arrows designated 34. The material to be pulped or otherwise treated mechanically is then charged into the vessel usually in chunks, bales or other large pieces. The proportion of solids to liquid is preferably such as to produce an ultimate suspension of high density.

Air or gas under pressure is admitted through the conduit 54 and fills the chamber 52 completely, after which the air or gas commences to flow outwardly around the lower edge of the rotating vertical flange 50, as indicated by the arrows 9h. The gas flowing around the bottom of the flange 50 will flow into the annular chamber but cannot escape vertically therefrom through opening 71 because it is met by the greater dynamic pressure of the liquid material being forced through opening 71 in the opposite direction as indicated by the arrow 80. The gas escapes from the chamber 76 in the direction of low pressure following the direction of arrow 82 joining the flow of deflected liquid moving in the same direction and the liquid and gaseous mixture then flows out from beneath the horizontal flange 62 in the direction of the arrow 84, through the passage 83.

In operation the layer of gas interposed between the under surface of the rotor disc 20 and the surrounding liquid frees the disc of the friction that would otherwise be created between the lower surface of the disc and the surrounding liquid during the rotation of the disc. In

practice I have found that the gas layer thus provided reduces substantially the power required to rotate the disc without in any way diminishing the effectiveness of the apparatus for vigorously agitating the material with which the vessel is charged.

The air entrapped in the chamber 70 is also efiective to reduce the friction between the rotor and the surrounding liquid. The rotor vanes 30 throw the liquid, such as the pulp suspension, against the edge of the ring 72. Some pulp will be deflected and pass with considerable force through the narrow clearance space, following the path shown by arrow 80. However, any liquid or pulp suspension which is forced against the outersurfacesof the rotating vertical flange 50 isthrown outwardly through the' gas within the chamber 76 ulti-' mately to flow to the bottom of the" annular chamber 70*and. thence outwardly with the gas through the course designated by arrows 82 and 84. Thus a mixture of gas. and liquid material will flow continuously in the direction=of arrow 84 beingeventually drawn into the general circulation of the: vessel indicated by arrows 34.

His: a-feature of my invention that the apparatus is substantiallyrelieved of the power demand heretofore impo'sedvby friction between the liquid and those parts ofi'the rotor surface which do no. effective work in the intense? agitation of the. mix'which the apparatus performs; As the result of my'invention, a considerably greater'proportion of the horsepower consumed is utilized in'work done between theupper vaned surface-of the disc and the liquid-solids suspension in contact therewith.

I claim:

1. In apparatus of the" character described the combination of a vessel adapted to containacharge of liquid chamber for the retention of a layer of gas contiguous to the under surface of 'the'disc and between it and-the surrounding liquid, a second annular flange surrounding the first annular flange concentrically therewithand stationarily mounted to'form an annular chamber with the first flange adaptedto receive gas overflowing from the first chamber aroundthe' lower extremity of the first flange, the second flange extending downwardly below the-lower extremity-of the'first flange to restrain the :escape of gas downwardly from the annular chamber and means for restraining theescape of gas upwardly from the annular chamber.

2. In apparatus of the character described the combination of a vessel adapted'to contain a charge of liquid material, a-rotor impeller disc located within the vessel for submerged rotation in the liquid and having vanes on its upper surface'for mechanicallyagitating the liquid material within the vessel, means for rotating the imr peller disc, a'conduit leading into proximity to the undersurface'of thedisc for conducting gas thereto, a dependingannular'flange in proximity to the outer periphery of the disc to'restrain the flow of gas out from under the disc, an annular chamber laterally surrounding the flange above the lower edge'of the flange to receive and confine thegas escaping around the lower edge of the flange, passage means'in' the upper part of the chamber in communication with the interior of" the vessel for conducting liquid downwardly into the chamber from the vessel, and passagemeansforrning' a communication between the lower'portion. of the chamber and the interior'of the vessel adjacentits side walls for conducting a mixture of liquid and gas from the chamber-into the interior of the vessel, whereby the rotational friction betweenthe impeller'disc and the surrounding liquid is reduced'by the maintenance of a film of gas between the lower surface of the disc and the surrounding liquid and"b'etv\'een the inner and outer surfaces of the flange and the surrounding liquid.

the combination of a vessel adapted to contain a charge of the mixture to be agitated, an impeller located in the vessel for submersion in the liquid with which the vessel is charged, a series of vanes on the upper surface of the impeller to subject the mixture to an intense frictional agitation as the impeller is rotated, the lower surface of the impeller being devoid of vanes, power supply means for driving the impeller with a rotary motion with a force adaquate to drive the vanes through the mixture to efiect such agitation, and means for minimizing the power consumed by friction from the said lower surface of the impeller during its rotation, said means comprising meansfor delivering gas in proximity to said lower surface, a substantially impervious wall for restraining escape of the gas so delivered to provide a constantly retained layer of gas between said lower surface and the surrounding liquid and means cooperating with said substantially impervious wall for inhibiting the escape of gas from the periphery of the impeller into the surrounding liquid.

4. In a low power consumption agitator for subjecting liquid-solid mixtures to an intense mechanical agitation, the combination of a vessel adapted to contain a charge of the mixture to be agitated, an impeller, in the form of a flat circular plate, located in the vessel for submersion in the liquid with which the vessel is charged, an series of vanes on the upper surface of the impeller to U subject the mixture to an intense frictional agitation as the impeller is rotated, the lower surface of the impeller.

being devoid-of vanes, power supply means for driving the: impeller with a rotary motion with a force adequate to drive the-vanes through the mixture to effect such 7 3. In a low power consumption agitator for sub ecting liquid-solidmixtures to'an' intense mechanical agitation,

agitation, means for delivering gas in proximity to said lower'surface, and a substantially impervious annular flange depending substantially normally from said flat circular plate to restrain escape of the gas so delivered and to retain a layer of gas between said lower surface and the surrounding liquid to minimize the friction of rotational movement of said surface.

5 In a low power consumption agitator for subjecting liquid-solid mixtures to an intense mechanical agitation, the combination of a vessel adapted to contain-a charge of the mixture to be agitated, an impeller in the form of a'flat circular disc located in the vessel for submersion in the liquid with which the vessel is charged, a series of vanes on the upper surface of the impeller disc to subject the mixture to an intense frictional agitation as the impeller is rotated, the lower surface of I the impeller discbeing devoid of vanes, power supply means for drivingthe'impeller with a rotary motion with a force adequate todrive'the'vanes through the mixture to effect such'agitation, means-for delivering gas in proximity to said lower surface, a substantially impervious annular flange depending substantially normally from said flat circular disc to restrain escape of the gas so delivered and toretain a layer of gas between said lower surface and the'surrounding liquid to minimize the friction of rotational movement of said surface, a stationary annular ring surrounding the disc and projecting into close proximity to the said upper surface carrying the said vanes, and a second annular flange stationarily mounted and depending from said ring to form an annular chamber surrounding said first flange to minimize the friction of rotation of saidfirst flange by retaining a supply of gas in contact with. the outer surface of said first flange.

References Cited in the file of this patent UNITED STATES PATENTS 572,304 Kleemann Dec. 1, 1896 2,055,065 Booth Sept. 22, 1936 2,265,936 Cowles Dec. 9, 1941 

